K3 - LO CUT/HI CUT bugs
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Up until recently, I had only used the SHIFT/WIDTH functions for
setting the DSP filter parameters. This morning I decided to try the LO CUT/HI CUT functions. I really don't understand the behavior I'm seeing and I suspect there's something wrong. I'm using FW 2.67 and DSP 1.96. I have the FM filter in FL1, and the 2.7KHz filter in FL2. No other filters currently installed. Both the FM and 2.7K filters are enabled for SSB and CW Rx. I'll start with SSB mode. I expected the LO and HI values to be independently adjustable with the only limitation that the HI value must be higher than the LO value. However, I find that for HI values greater than 2.70, the maximum LO value I can dial in is lower, Hz for Hz. In other words, the LO and HI limits track in opposite directions when the HI value is > 2.70. Example: HI value Max LO value 2.70 2.50 2.80 2.40 2.90 2.30 3.00 2.20 3.10 2.10 ... ... 4.10 1.10 With the HI value 2.70 or lower, the maximum LO value is always 0.20 less than the HI value, which seems reasonable. Trying to use LO/HI CUT mode in CW mode reveals the same sort of behavior described above except the HI value where the controls start the divergent tracking is 1.05. There are a lot of other odd behaviors in CW mode that simply don't make any sense. E.g. the LO and HI values can be set to the same value (e.g. 1.00 and 1.00). I suspect the actual bandwidth in this case is 50 Hz. Not a biggie but I would expect the closest separation in the displayed values to be 50 Hz (0.95 and 1.00). E.g. if I start in SHIFT/WIDTH mode with BW=2.80 and FC=1.10 and then switch to LO/HI mode, the maximum HI value I can set is 2.50. If I start with BW=2.8 and FC=0.60 then switch, the maximum HI value I can set is 2.00. Various other BW and FC settings result in other maximum HI values. E.g. if I start with BW=2.8/FC=0.60 then switch, the MINIMUM HI value I can set is 1.00, UNTIL I activate the LO control (e.g. by turning it counterclockwise, which doesn't actually change the current value of 0.00), then I can set HI values lower than 1.00. E.g. Depending on the exact BW/FC values I start with, when I switch, sometimes the LO and HI values are at a 50 Hz boundary. That is, 2.15 instead of 2.10, and the step size seems to always be 100 Hz (2.15 -> 2.05 -> 1.95 etc.) These oddities aren't apparent in normal day-to-day operation, but I think they're pretty clearly unintended. 73 -- Joe KB8AP _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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Hello Joe!
> Up until recently, I had only used the SHIFT/WIDTH functions for setting > the DSP filter parameters. This morning I decided to try the LO CUT/HI > CUT functions. I really don't understand the behavior I'm seeing and I > suspect there's something wrong... > > These oddities aren't apparent in normal day-to-day operation, but I > think they're pretty clearly unintended. Thank you for your investigation and detailed observations of this. We've taken note of it and put it "on the list" to be corrected. Hope you have a great Thanksgiving Holiday! 73, Lyle KK7P _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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In reply to this post by Joe Planisky
Is this really a case that something is broken or is it that the operation needs to be explained better?
If you set the BW to a very narrow width, THEN, switch over to adjust the HI and/or LO CUT, things seem to work as I would expect. It appears to me that the HI/LO CUT is associated with the center frequency and not that the LO cut is associated with the HI CUT or vice versa. Since the K3 has a minimum (minimal) amount of front panel controls some of the controls function is counter intuitive. Rich, KE0X
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In reply to this post by Joe Planisky
Hi,
I can confirm this behavior. I have never noticed this because as an SSB operator I always use a low cut of either 200, 300 or 400. I generally leave low cut at 300Hz and use high cut as a QRM fighting tool. Since most CW operators use the SHIFT/WIDTH mode, that is probably is another reason why this has gone undetected. BTW the graphic passband representation is also pretty screwed up when changing back and forth between shift/width and hicut/locut modes. In particular, changing the hi cut often moves the left edge of the graphics when switching between the modes. I can provided a detailed scenario if it helps.
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In reply to this post by Rich
While this isn't a major issue, it will be nice to have it operate more
smoothly and predictably. The issue has been on the firmware "list" for some time now but other enhancements and improvements have taken priority. Even though I personally would like this issue addressed, I strongly support Elecraft engineering putting emphasis where they have been. In general, WIDTH/SHIFT are best applicable to CW and DATA modes while HI CUT/LO CUT fit SSB better. When I want to narrow my RX SSB bandwidth, I reduce HI CUT because that simultaneously narrows the bandwidth and moves Fc down at half the rate which is exactly where I want the narrower bandwidth located in the audio passband. (Using WIDTH requires a correlated adjustment of SHIFT while searching for the best intelligibility. I find this much more difficult and time-consuming than simply reducing HI CUT. LO CUT never needs to be touched until you get to SSB bandwidths lower than about 1.5 kHz.) Narrowing WIDTH, then switching to LO CUT/HI CUT, etc. is not a viable solution for quick bandwidth changes on SSB. One of my K3s is has nominal LO CUT at 250 Hz while the other one is at 300 Hz, with both having increments of 100 Hz. This is a minor annoyance, not a major problem. To that point, I don't spent time trying to keep them the same. It just doesn't matter much and I'd rather spend the time operating. Ed Rich, KE0X replied: > Is this really a case that something is broken or is it that > the operation needs to be explained better? > If you set the BW to a very narrow width, THEN, switch over > to adjust the HI and/or LO CUT, things seem to work as I > would expect. > It appears to me that the HI/LO CUT is associated with the > center frequency and not that the LO cut is associated with > the HI CUT or vice versa. > Since the K3 has a minimum (minimal) amount of front panel > controls some of the controls function is counter intuitive. > > Rich, > KE0X > > > Joe Planisky wrote: > > > > Up until recently, I had only used the SHIFT/WIDTH functions for > > setting the DSP filter parameters. This morning I decided > to try the > > LO CUT/HI CUT functions. I really don't understand the > behavior I'm > > seeing and I suspect there's something wrong. > > > > > > _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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In reply to this post by KK7P
A potentially related question / mis-understanding is the interaction
between width, shift, lo and hi. I'm not sure my concept is correct... Firstly, people talk about 5 frequencies or ranges: Fc = audio center of the passband Fhi = -3 dB point above Fc Flo = -3 dB point below Fc Fshift Fwidth = passband width between -3 dB points but I think there are also two other frequencies: Ffloor = lowest permitted frequency for a -3 dB point. Let's assume this is 100 Hz. Fanchor = a reference frequency that is a conceptual point-of-return for the center. In CW this is Fspot and in sideband this is a passband center when the passband is narrow enough that the lower edge is above Ffloor. CW example: Start with a spot of 400 Hz and a filter setting of 500 Hz. Fc = 400 Hz Fanchor = Fspot = 400 Hz Flo = 150 Hz Fhi = 650 Hz Fshift = 0 Fwidth = 500 Hz Under my mental picture, Shift moves the passband away from the Fspot (Fanchor). A shift of +100 Hz to move away from adjacent QRM changes the picture to: Fshift = +100. Fwidth = 500 Hz Fanchor = Fspot = 400 Hz (unchanged) Fc = 500 Hz Flo = 250 Hz Fhi = 750 Hz If one attempts to shift -100 Hz, Flo runs into the Ffloor value. Since the operator presumably is trying to evade QRM on the high side, what should be done? One approach is to allow the passband to narrow: Fshift = -100 Fanchor = Fspot = 400 Hz Flo = 100 Hz (stopped at the floor) Fhi = 550 Hz Fc = 325 Hz Fwidth = 450 Hz. SSB example: Start with 2.8 kHz width, with -3 dB points of 200 and 3000 Hz. Flo = 200 Hz Fhi = 3000 Hz Fc = 1600 Hz Fwidth = 2.8 kHz Fshift = 0 Fanchor = 1600 kHz (reference point for the shift) Now suppose one wants to operate in a contest environment. Set the radio to always use a 1.8 kHz filter. But, rather than listen to a too-low range of 200 - 2000 Hz, center the passband around 1600 Hz: Flo =700 Hz Fhi = 2500 Hz Fc = 1600 Hz Fwidth = 1800 Hz Fshift = 0 Fanchor = 1600 Hz Now increase the width control to 2200 Hz. The signal still passes through the 1.8 kHz filter. So the parameters are: Flo = 500 Hz Fhi = 2700 Hz Fc = 1600 Hz = Fanchor Fwidth = 2200 Hz Fshift = 0 This sounds quite acceptable in a contest: very intelligible but not troubled as much by adjacent stations as the wider crystal filter choices. Manipulating the shift, width, lo and hi frequencies allow deviations from the above... but zeroing the shift always returns Fc to the anchor frequency. I don't think the radio quite works this way. And maybe this isn't the correct model. But hopefully it's a constructive addition to the conversation. -- Eric K3NA on 08 Nov 26 Wed 15:06 Lyle Johnson said the following: > Hello Joe! > >> Up until recently, I had only used the SHIFT/WIDTH functions for >> setting the DSP filter parameters. This morning I decided to try the >> LO CUT/HI CUT functions. I really don't understand the behavior I'm >> seeing and I suspect there's something wrong... >> >> These oddities aren't apparent in normal day-to-day operation, but I >> think they're pretty clearly unintended. > > Thank you for your investigation and detailed observations of this. > We've taken note of it and put it "on the list" to be corrected. > > Hope you have a great Thanksgiving Holiday! > > 73, > > Lyle KK7P > Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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